The present invention is directed to a shock absorber for dampening the initial effect of relatively quick stopping and starting of a heavily loaded trolley or trolleys on a conveyor system, especially a power and free conveyor system.
Much of the assembly work done at various manufacturing plants and much of partially assembled or fully assembled transport of goods around a plant is by conveyor systems. In particular, partially completed goods or finished goods are placed on carriers with wheeled trolleys and conveyed about a plant on one type of conveyor system or another, especially the types of conveyor systems known as power and free conveyor systems. When the trolleys carrying a load come to a location where work is to be accomplished, or where the goods are simply to be accumulated, or where a moving trolley must stop because of a previously stopped trolley in front of it, etc., the trolleys and the loads on the trolleys must decelerate at a very high rate. Likewise, the drive units for such conveyors typically operate at a constant speed and loaded trolleys must almost instantly move at the speed of the driver, thereby placing stress on the conveyor parts and the goods being conveyed.
Because conveyor systems of the type described herein are utilized to transport many large and heavy items, such as washing machines, dishwashers, refrigerators, automobiles and trucks, sometimes weighing as much as 10,000 pounds each, almost instantaneous stopping and starting of the trolleys can cause damage to the loads as they try to continue in motion when stopping, or accelerate when starting. Over time this causes substantial damage to the conveyor system itself. Conveyor systems that utilize no dampening within the system very rapidly deteriorate, especially as the weight of the loads carried by the trolleys increases. Consequently, it has been recognized for some time by the conveyor industry that it is desirable to dampen the effect of the very rapid stops and starts required by many systems. This is normally accomplished by providing a lead or drive trolley which is in turn selectively driven by a driving mechanism such as a dog attached to a continuously moving chain. The drive trolley in turn is connected by a tow bar to one or more load carrying trolleys which actually support the goods being conveyed. The tow bar includes some type of dampening mechanism for reducing the stress applied to the load carrying trolleys and the load carried thereby during a quick stop or start.
The inventor of the present application has been the inventor or co-inventor of a number of different patents directed to shock absorbing devices of the type described herein, such as U.S. Pat. No. 3,330,953. Applicant has found that there is an ever increasing desire to provide a simple shock absorbing mechanism that is highly effective in dampening the effect of sudden stops and starts on the conveyor trolleys.
It has also been found that it is necessary to be able to adjust the strength of the dampening mechanism in correspondence to the weight of the load being carried by the trolleys. Where the dampening mechanism is the result of some type of resistance or friction producing mechanism, a very high resistence will result in effectively no dampening when used with very light loads, because the dampening system will never operate, whereas a light dampening resistence will have virtually no effect on dampening relatively heavy loads, because the weight of the load will overcome the resistance so easily that there will be no effective resistance, and consequently, no effective dampening. Therefore, it is also desirable to have a dampening mechanism in which the resistance can be relatively easily changed to adjust for the particular loads being carried by the trolleys. While certain prior art dampening systems for this type of device have allowed for adjustment, such adjustment has required disassembly of the dampening mechanism to such an extent that it has not been relatively easy to accomplish the change without essentially taking everything apart. Consequently, it is also desirable to have a dampening mechanism wherein adjustments can be made relatively easily when the conveyor is first placed in use, when loads on the system change, and after such a period of time when wear and tear reduces or increases resistance.